A novel reflective image display using total internal reflection

We are developing a new reflective display technology, based on total internal reflection, which achieves a large difference between the maximum and minimum reflectance values. This yields a surface with greatly improved legibility under a wide range of illumination conditions. Such devices can display an image with a maximum reflectance ranging from 55% under uniform background illumination to over 85% under common non-uniform illumination conditions, even at viewing angles greater than 80° from the surface normal. This approach, which we call ‘CLEAR’ (Charged Liquid Electro-Active Response), uses polymeric microstructures to efficiently redirect incoming ambient light back toward the viewer. One advantage of this technique is the ability to achieve bright, full-color images over a wide range of viewing angles, much like ink printed on paper. The displayed image can be updated rapidly since switching from the reflective state to the absorptive state requires only about a half-micron of motion of absorbing material into the evanescent field associated with TIR. This new approach offers significant advantages in a number of reflective display applications.     

Filament-Free Bulk Resistive Memory Enables Deterministic Analogue Switching

Digital computing is nearing its physical limits as computing needs and energy consumption rapidly increase. Analogue-memory-based neuromorphic computing can be orders of magnitude more energy efficient at data-intensive tasks like deep neural networks, but has been limited by the inaccurate and unpredictable switching of analogue resistive memory. Filamentary resistive random access memory (RRAM) suffers from stochastic switching due to the random kinetic motion of discrete defects in the nanometer-sized filament. In this work, this stochasticity is overcome by incorporating a solid electrolyte interlayer, in this case, yttria-stabilized zirconia (YSZ), toward eliminating filaments. Filament-free, bulk-RRAM cells instead store analogue states using the bulk point defect concentration, yielding predictable switching because the statistical ensemble behavior of oxygen vacancy defects is deterministic even when individual defects are stochastic. Both experiments and modeling show bulk-RRAM devices using TiO_2-X switching layers and YSZ electrolytes yield deterministic and linear analogue switching for efficient inference and training. Bulk-RRAM solves many outstanding issues with memristor unpredictability that have inhibited commercialization, and can, therefore, enable unprecedented new applications for energy-efficient neuromorphic computing. Beyond RRAM, this work shows how harnessing bulk point defects in ionic materials can be used to engineer deterministic nanoelectronic materials and devices.     

Electron paramagnetic resonance spectroscopic measurement of Mn2+ binding affinities to the hammerhead ribozyme and correlation with cleavage activity

Efficient phosphodiester bond cleavage activity by the hammerhead ribozyme requires divalent cations. Toward understanding this metal ion requirement, the Mn2+-binding properties of hammerhead model ribozymes have been investigated under dilute solution conditions, using electron paramagnetic resonance spectroscopy (EPR) to detect free Mn2+ in the presence of added ribozyme. Numbers and affinities of bound Mn2+ were obtained at pH 7.8 (5 mM triethanolamine) in the presence of 0, 0.1, and 1.0 M NaCl for an RNA-DNA model consisting of a 13-nucleotide DNA "substrate" hybridized to a 34-nucleotide RNA "enzyme" [Pley, H. W., Flaherty, K. M., and McKay, D. B. (1994) Nature 372, 68-74]. In 0.1 M NaCl, two classes of Mn2+ sites are found with n1 = 3.7 +/- 0.4, Kd(1) = 4 +/- 1 microM (type 1) and n2 = 5.2 +/- 0.4, Kd(2) = 460 +/- 130 microM (type 2). The high-affinity type 1 sites are confirmed for an active RNA-RNA hybrid (34-nucleotide RNA enzyme:13-nucleotide RNA substrate) by EPR measurements at low Mn2+ concentrations. Decreasing NaCl concentration results in an increased number of bound Mn2+ per hammerhead. By contrast, a binding titration in 1 M NaCl indicates that a single Mn2+ site with apparent Kd approximately 10 microM is populated in low concentrations of Mn2+, and apparent cooperative effects at higher Mn2+ concentrations result in population of a similar total number of Mn2+ sites (n1 = 8-10) as found in 0.1 M NaCl. Mn2+-dependent activity profiles are similar for the active RNA-RNA hybrid in 0.1 and 1 M NaCl. Correlation with binding affinities determined by EPR indicates that hammerhead activity in 0.1 M NaCl is only observed after all four of the high-affinity Mn2+ sites are occupied, rises with population of the type 2 sites, and is independent of Mn2+ concentrations corresponding to > 8-9 Mn2+ bound per hammerhead. Equivalent measurements in 1 M NaCl demonstrate a rise in activity with the cooperative transition observed in the Mn2+ binding curve. These measurements indicate that, over this NaCl concentration range, hammerhead ribozyme activity is influenced by population of a specific set of divalent cation sites.     

The role of SAPL as a boundary lubricant in prosthetic joints

The purpose of this study was to test the potential of the body's natural lubricant, surface-active phospholipids (SAPL), to decrease friction in prosthetic joints by acting as a boundary lubricant, and to test the interaction of SAPL with Pyrolytic Carbon (PyC), a new material used in artificial heart valves and joint replacements of the upper limb. Initial testing [Coller R, Hargreaves DJ, Hills BA, Crawford RW. Is SAPL the boundary lubricant in prosthetic joints: friction testing and surface rinsing. Australian Journal of Mechanical Engineering 2004;1:63–71] slid ultra-high molecular weight polyethylene (UHMWPE) pins against highly polished stainless steel plates (surface roughness of 0.01 μm). This second series of tests was a continuation of previous research, validating the results and expanding the experiments to investigate the interaction of SAPL with PyC. In both cases, a Hounsfield test rig was used to perform the tests at ambient room conditions and at 37 °C. In both series of tests, comparative friction measurements were made using a synthetic SAPL, dipalmitoyl phosphatidylcholine (DPPC) with saline and saline only as the lubricants. When DPPC was used, the friction was reduced by 50% for the UHMWPE/SS combination, and was reduced by more than 75% for the UHMWPE/PyC combination, suggesting that DPPC acts as an effective boundary lubricant. This recent study, along with previous testing [Coller R, Hargreaves DJ, Hills BA, Crawford RW. Is SAPL the boundary lubricant in prosthetic joints: friction testing and surface rinsing. Australian Journal of Mechanical Engineering 2004;1:63–71], strongly suggests that SAPL has the ability to decrease friction in prosthetic joints by acting as a boundary lubricant, and that SAPL interacts favourably with PyC.     

Predicting Control Performance of Residential Heating Systems with an Analog Computer

A properly designed residential heating system must provide homeowner comfort under a broad range of operating conditions. Doing this with an economically priced system requires knowledge of the many variables affecting system performance. A typical heating system including the house, furnace, heat conveyance, and thermostatic control has been simulated on an analog computer facility. By varying computer inputs to reflect changing outdoor weather conditions, house construction, type of heating plant, and occupancy, system performance with different types of controls can be readily evaluated. This type of computer analysis facilitates early consideration of component design variations aimed at achieving optimum performance with minimum cost.     

Nanoscale scraping and dissection of collagen fibrils

The main function of collagen is mechanical, hence there is a fundamental scientific interest in experimentally investigating the mechanical and structural properties of collagen fibrils on the nanometre scale. Here, we present a novel atomic force microscopy (AFM) based scraping technique that can dissect the outer layer of a biological specimen. Applied to individual collagen fibrils, the technique was successfully used to expose the fibril core and reveal the presence of a D-banding-like structure. AFM nanoindentation measurements of fibril shell and core indicated no significant differences in mechanical properties such as stiffness (reduced modulus), hardness, adhesion and adhesion work. This suggests that collagen fibrils are mechanically homogeneous structures. The scraping technique can be applied to other biological specimens, as demonstrated on the example of bacteria.     

基于全内反射和减色滤波法的新型反射式彩色显示技术

我们提出了采用减色滤光膜（subtractive color filltering)装置控制棱镜微结构全内反射（Total Interal Reflection,TIR)的一种反射式彩色显示技术。这种棱镜的表面能够有效地改变射向观察者的环境光线的方向而减色。采用减色波光法能得到明亮而易辨认的低功耗彩色图象,它比常规RGB反射式彩色LCD显示的反射率改善了4倍。该技术的主要优点是仅用约半微米起伏（about a half-micron movement）的可控减色滤波膜就能够在高反射和亮彩色态之间进行转换。     

Parameter Optimization Studies for a Tandem Mirror Neutron Source

A basic plasma physics tandem mirror experiment is proposed to develop the potential uses of magnetic mirror confined plasmas for a neutron source. We consider parameter variations from the currently operating symmetric mirror plasma trap GDT in an attempt to optimize the neutron source intensity while minimizing the expense and complications of the system. The combined radial and axial plasma loss rates are analyzed and shown to yield an optimal operational point that minimizes the required auxiliary heating power.